Video: TODAY celebrates Pi Day with blindfolded pie tasting

It’s a different sort of holiday: Pi Day, which celebrates the mathematical constant pi, the ratio of a circle's circumference to its diameter. To celebrate, BuzzFeed’s Emily Fleischaker offers delicious recipes for three different pies.

Preparation

To make crust:
Preheat the oven to 350°F. Grease a 9-inch pie pan with butter or baking spray. Put pretzel sticks in a food processor and process for about 30 seconds. (Or put in a plastic bag and whack at them with the back of a spoon until they are in small crumbs.) Put the crumbs into a bowl then add the sugar and melted butter, mixing to combine. Press the mixture into the bottom and up the sides of the prepared pan. Bake for 8 to 10 minutes — the crust shouldn't change color too much but it will set. Then freeze crust for 30 minutes while you make the caramel.

To make caramel sauce:Put sugar and water into a saucepan (try not to get any sugar or water on sides of pan) over medium low heat and stir until sugar has dissolved. Dissolve any crystals forming on the side with a wet pastry brush. Once sugar has dissolved increase heat to high. At this point, don't stir the mixture anymore. It will start to bubble after a minute and you should occasionally take the pan's handle and swirl it to keep the syrup moving. Once the syrup starts to turn a light gold, add the butter and heavy cream. The mixture will bubble wildly and that's normal.

Whisk to combine. Set aside.

To make chocolate ganache:Combine 1 1/3 cup chocolate chips, 2/3 cup cream, corn syrup, and 1 teaspoon vanilla in microwave-safe bowl. Microwave on medium heat until chocolate softens, about 3 minutes. Whisk until melted and smooth. (You can also do this in a saucepan - just combine everything and heat over medium heat, whisking occasionally, until melted and combined.) Spread chocolate mixture over bottom of crust. Freeze 20 minutes.

To make peanut butter mousse:Microwave peanut butter chips and 3/4 cup cream in large microwave-safe bowl on medium heat at 15-second intervals just until chips soften, stirring often. (Same goes here for doing this in a saucepan.) Whisk in peanut butter and 1 teaspoon vanilla. Set aside to cool.

Using a whisk or electric beater, beat remaining 1 cup cream and 2 tablespoons sugar in medium bowl until very thick and just holding peaks. Once peanut butter mixture is cool, gently fold the whipped cream into the peanut butter mixture.

To assemble:
Cover chocolate layer with caramel (you may want to reheat and whisk caramel to get it "moving" before you add it), and freeze 20 minutes.

Preparation

For the crust:

1. Measure out all of your ingredients for the crust and make sure your butter
and shortening are very cold. (It helps to put them in the freezer after they're
measured and cut into pieces. It also helps to keep the flour in the freezer.)

2. Put flour, butter, vegetable shortening, sugar, and salt in a food processor and
pulse JUST until butter resembles tiny pebbles, about 12-15 times. (If you don't
have a food processor, stir the dry ingredients then cut the fats into the mixture
with the tines of a fork until you have tiny pebbles and it's pretty well
incorporated.) Transfer to a large bowl. Gradually add vinegar-ice water mixture,
using a fork to stir until dough is a mixture of clumpy wet pieces and sandy
pieces, adding more water if dry. Take care not to over-moisten your dough -
you don't have to use all ¾ cups liquid. Watch the dough and stop adding liquid
once it begins to clump. It doesn't need to be completely stuck together.

3. Turn dough out onto a clean counter and form into ball. Be careful not to over
handle it -- it doesn't need to be kneaded, just needs to come together. Once it's
in a ball, cut the ball in half then flatten the halves into discs. Wrap each disc in
plastic wrap and chill at least 1 hour or overnight. (DO AHEAD Can be made
ahead. Keep dough refrigerated up to 2 days, or enclose in resealable plastic bag
and freeze up to 1 month, then thaw in refrigerator overnight. Soften slightly at
room temperature before rolling out.

5. Prepare a clean counter top as workspace to roll out the dough. Sprinkle some
flour on a sheet of parchment, put one dough disc on it, then sprinkle flour on the
disc, then top with another sheet of parchment. Using a rolling pin, roll out
dough between those two sheets of parchment paper in a circular shape until its
diameter is 2"-3" larger than the pie plate all around.

6. Remove the top sheet of parchment then carefully pick up an edge of the
round and wrap it around the rolling pin. As you continue to roll the pin, the
dough will wrap completely around it so you can pick easily transfer it to the
plate. Starting on one edge of the pie plate, unroll the dough, making sure it is
centered. At this point it's best to put it back in the fridge for 30 minutes to 1
hour.

7. Press the dough into the plate. Leaving enough dough to crimp the edges, trim
the overhang with a knife or scissors.

8. Preheat oven to 375°F. Prick chilled crust in pie dish all over with a fork. Line
crust with foil or parchment paper, then fill the liner with dried beans or pie
weights. Bake 25 minutes. Remove from oven; lift out foil and weights. Reduce
temperature to 350°. Return to oven and bake, using fork to prick any bubbles
that have formed and pressing down on them with back of fork, until crust is
JUST light golden brown, about 2 minutes longer. (It will bake again later so it
shouldn't be too dark yet.) Let crust cool completely.

For mac and cheese filling:

1. Boil pasta in generously salted water until just al dente, following directions on
package.

2. Cook bacon pieces in sauté pan until just crispy, drain on paper towels and set
aside.

3. In a large pot, melt the butter. Then stir in the flour. Whisk to combine and
cook for 1-2 minutes. Now you've got what is called a "roux" - equal parts
butter and flour cooked together. Add the cream and whisk again, let cook,
whisking occasionally, for 5-10 minutes until it thickens. Now you've got
bechamel sauce.

4. Add mustard powder and whisk to combine.

5. Temper egg yolk into the bechamel -- to do this, take a little of your hot
bechamel and put it into a bowl with the egg yolk. Whisk so that the egg heats up
gently. Then dump the warm egg/bechamel mixture into the hot pot of bechamel,
and whisk.

6. Add all the cheese and stir to combine. Season with salt and freshly ground
pepper.

Preparation

For the crust:

1. Measure out all of your ingredients for the crust and make sure your butter
and shortening are very cold. (It helps to put them in the freezer after they're
measured and cut into pieces. It also helps to keep the flour in the freezer.)

2. Put flour, butter, vegetable shortening, sugar, and salt in a food processor and
pulse JUST until butter resembles tiny pebbles, about 12-15 times. (If you don't
have a food processor, stir the dry ingredients then cut the fats into the mixture
with the tines of a fork until you have tiny pebbles and it's pretty well
incorporated.)

Transfer to a large bowl.

Gradually add vinegar-ice water mixture, using a fork to stir until dough is a mixture of clumpy wet pieces and sandy pieces, adding more water if dry.

Take care not to over-moisten your dough - you don't have to use all ¾ cups liquid. Watch the dough and stop adding liquid once it begins to clump. It doesn't need to be completely stuck together.

3. Turn dough out onto a clean counter and form into ball. Be careful not to over
handle it -- it doesn't need to be kneaded, just needs to come together. Once it's
in a ball, cut the ball in half then flatten the halves into discs. Wrap each disc in
plastic wrap and chill at least 1 hour or overnight. (DO AHEAD Can be made
ahead. Keep dough refrigerated up to 2 days, or enclose in resealable plastic bag
and freeze up to 1 month, then thaw in refrigerator overnight. Soften slightly at
room temperature before rolling out.

5. Prepare a clean counter top as workspace to roll out the dough. Sprinkle some
flour on a sheet of parchment, put one dough disc on it, then sprinkle flour on the
disc, then top with another sheet of parchment. Using a rolling pin, roll out
dough between those two sheets of parchment paper in a circular shape until its
diameter is 2"-3" larger than the pie plate all around.

6. Remove the top sheet of parchment then carefully pick up an edge of the
round and wrap it around the rolling pin. As you continue to roll the pin, the
dough will wrap completely around it so you can pick easily transfer it to the
plate. Starting on one edge of the pie plate, unroll the dough, making sure it is
centered. At this point it's best to put it back in the fridge for 30 minutes to 1
hour.

7. Press the dough into the plate. Leaving enough dough to crimp the edges, trim
the overhang with a knife or scissors.

8. Preheat oven to 375°F. Prick chilled crust in pie dish all over with a fork. Line
crust with foil or parchment paper, then fill the liner with dried beans or pie
weights. Bake 25 minutes. Remove from oven; lift out foil and weights. Reduce
temperature to 350°. Return to oven and bake, using fork to prick any bubbles
that have formed and pressing down on them with back of fork, until crust is light
golden brown, about 10 minutes longer. Let crust cool completely.

For the filling:

1. Set a medium bowl over a large bowl of ice. Place a strainer in bowl; set aside.

2. Fill a medium bowl with ice and water. Cook peas in rapidly boiling water for 3
minutes, then drain cooked peas and transfer to ice bath. Once peas are cool
(after 2-3 minutes), drain and set aside.

3. In a medium saucepan over medium heat, cook milk, 1/4 cup sugar, vanilla
bean and seeds, and salt until mixture comes to a simmer.

4. Scoop ½ cup of milk mixture into a bowl and let cool. Once cool, put in a
blender with cooked peas. Puree until smooth.

5. In a medium bowl, whisk together egg yolks, cornstarch, and remaining 1/2
cup sugar. Whisking constantly, slowly pour about 1/2 cup of the hot-milk
mixture into the egg-yolk mixture, 1/2 cup at a time, until it has been
incorporated. Pour mixture back into saucepan, and cook over medium-high
heat, whisking constantly, until it thickens and you see maybe one bubble break
the surface, about 5 minutes. Remove and discard vanilla bean. Congrats, you've
made pastry cream!

4. Strain pastry cream into the bowl that's over the large bowl of ice. Cover with
plastic wrap, pressing it directly onto the surface of the pastry cream to prevent a
skin from forming. Once it's cool (about 30 minutes) strain pea puree into that
same bowl. Whisk to combine.

5. Pour sweet-pea pastry cream into baked pie crust until it comes ½ way up the
crust and refrigerate at least 2 hours and up to 24 hours to let the filling set. This
part is important so don't skip it or rush it! (DO AHEAD: Pastry cream will keep
separately for up to 2 days in an airtight container.)

For topping:
When you're ready to serve, stir jelly in heavy saucepan over low heat with water
until melted. Pile berry halves onto filling, brush with warm jelly to glaze, and
serve.